Compare two PDFs
Line-by-line differences between two versions of a document.
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Accepted formats: PDF
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Quick facts
- What it does
- Extracts the text of two PDFs and shows, line by line, what was added, removed or changed.
- Input
- Output
- A report on screen — no file is produced
- Processing
- In your browser
- Files uploaded?
- No
- Account required?
- No
- Best for
- Checking which pages changed between two versions of a contract or a draft.
- Main limitation
- It compares text, not appearance. A change to a font, a colour or an image is invisible to it, and a PDF with no text layer gives it nothing to read — run OCR on a scan first.
How to use this tool
- Upload both PDFs — the older one first.
- The text of each is read and lined up.
- Review the additions, removals and changes, page by page.
Why use iBuildPDF
Being sent "a small revision" of a twenty-page contract and being expected to spot it is a genuinely bad position to be in. A line-level comparison turns an hour of squinting into a minute of reading.
How it works
The text of both documents is extracted and compared line by line using a standard longest-common-subsequence diff, the same approach code review tools use. Both files stay in your browser.
Frequently asked questions
Does it compare images and layout?
No — it compares text. A moved logo or a changed font will not show up. Being clear about that is more useful than implying a visual comparison this tool does not do.
It says one of my files has no text.
That one is a scan, so there is nothing to compare against. Both documents need a text layer.
Is there a limit on how long the documents can be?
The comparison stops at 2000 lines per document. The matching start and end are trimmed away first, so two versions of the same contract rarely come close, but two unrelated long reports will. The cap exists because the work grows with the length of both documents multiplied together.
Can I download the result?
No. The differences are shown on screen and there is no report file to save — take a screenshot or copy the lines you need. Neither document is modified and nothing is written to your disk.
Why is a line marked as changed when the wording looks identical?
Because lines are rebuilt from where the text sits on the page, so a different line break, a changed font size or a reflowed paragraph moves where one line ends and the next begins. A layout change can therefore read as a text change.
Can I compare more than two files?
Two at a time. Choose the older version first, so that new wording reads as an addition rather than a removal. For a chain of revisions, compare each pair in turn.
Does it tell me which page a change is on?
Yes. Every line carries its page number, and only changed lines and a little context around them are listed rather than the whole document. For anything legal, going back to the page and reading the change in context is usually worth the extra minute.
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